PostgreSql psql 用法

一、 psql 介绍

  psql 是 PostgreSQL 中的一个命令行交互式客户端工具，类似 Oracle 中的命令行工具 sqlplus，它允许用户交互地键入 SQL 语句或命令。此外，它还提供了一些快捷命令和多种类似 Shell 的特性来实现书写脚本，便于对大批量任务的自动化操作。虽然 psql 的功能与 sqlplus 差不多，但使用起来远比 sqlplus 简便，如可以用上下方向键，把上一条和下一条 SQL 命令翻出来，还有单击 Tab 键自动补全功能。

二、连接进入交互界面

2.1 语法

psql [option...] [dbname [username]]

dbname username：数据库名 用户名（顺序不能错）如下所示：

[postgres@localhost ~]$ psql postgres postgres
psql (13.6)
Type "help" for help.

postgres=#

--有时 psql 后不加参数也可连接，原因为不带参数时，数据库及用户名默认值均为当前系统用户名，结果同上
[postgres@localhost ~]$ psql
psql (13.6)
Type "help" for help.

postgres=#

option可选项：

-h hostname 或 --host=hostname：连接地址。
-U username 或 --username=username：连接用户。
-d dbname 或 --dbname=dbname：连接数据库名。
-p port 或 --port=port：连接端口号。
-W 或 --password：回车后的交互界面强制输入口令，并不是该参数后跟口令，常用户后台脚本中，在脚本结尾配置，会使之前设置的所有免密登录失效。
-w 或 --no-password：回车后的交互界面从不输入口令，常用户后台脚本中，需配合密码参数使用，如 PGPASSWORD=postgres psql -w，在脚本结尾配置，会使之前设置的所有密码认证登录失效。
-c command 或 --command=command：连入交互界面执行sql命令后退出，常用与脚本中。
-f filename 或 --file=filename：连入交互界面执行 sql 文件后退出，常用于向数据库中导入 sql。等价于下述元命令中的 \i。
-o filename 或 --output=filename：把所有查询输出放到文件 filename 中。当前查询不显示内容，且 filename 文件中不包含查询 sql。等价于下述元命令中的 \o。
-L filename 或 --log-file=filename：除了把所有查询输出写到普通输出目标之外，还写到文件 filename 中。当前查询显示内容，且 filename 文件中包含查询 sql。
-E：连入交互界面执行快捷元命令时，显示对应 sql 语句。等效下述元命令中的 \set ECHO_HIDDEN on。
-V 或 --version：输出 psql 版本。
psql --help：显示 psql 使用帮助，有上述之外需求的，查询该使用帮助。

2.2 示例

--交互界面时输入密码（-W 为强制输入密码，即便配置了免密登录策略也强制输入）
psql -h 192.168.100.115 -U postgres -d postgres -p 5432
psql -h 192.168.100.115 -U postgres -d postgres -p 5432 -W

--交互界面时不输入密码
PGPASSWORD=postgres psql -h 192.168.100.115 -U postgres -d postgres -p 5432 -w

--可也通过设置如下环境变量后，再执行 psql 命令连入，效果同上
export PGHOST=192.168.100.115
export PGUSER=postgres
export PGDATABASE=postgres
export PGPORT=5432
export PGPASSWORD=postgres
psql

--连入交互界面执行sql命令后退出
psql -c 'select version();'
等价于
psql
select version();
\q

[postgres@localhost ~]$ psql -c 'select version();'
                                                 version
---------------------------------------------------------------------------------------------------------
 PostgreSQL 13.6 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit
(1 row)

[postgres@localhost ~]$ psql
psql (13.6)
Type "help" for help.

postgres=# select version();
                                                 version
---------------------------------------------------------------------------------------------------------
 PostgreSQL 13.6 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit
(1 row)

postgres=# \q
[postgres@localhost ~]$

--交互界面执行 sql 文件后退出
[postgres@localhost ~]$ cat select.sql
select * from emp;
[postgres@localhost ~]$ psql -f select.sql
 employee_id | first_name | last_name |  email   | phone_number | hire_date  |   job_id   |  salary  | commission_pct | manager_id | department_id
-------------+------------+-----------+----------+--------------+------------+------------+----------+----------------+------------+---------------
         100 | Steven     | King      | SKING    | 515.123.4567 | 2003-06-17 | AD_PRES    | 24000.00 |                |            |            90
         101 | Neena      | Kochhar   | NKOCHHAR | 515.123.4568 | 2005-09-21 | AD_VP      | 17000.00 |                |        100 |            90
         102 | Lex        | De Haan   | LDEHAAN  | 515.123.4569 | 2001-01-13 | AD_VP      | 17000.00 |                |        100 |            90
         103 | Alexander  | Hunold    | AHUNOLD  | 590.423.4567 | 2006-01-03 | IT_PROG    |  9000.00 |                |        102 |            60
         104 | Bruce      | Ernst     | BERNST   | 590.423.4568 | 2007-05-21 | IT_PROG    |  6000.00 |                |        103 |            60
         105 | David      | Austin    | DAUSTIN  | 590.423.4569 | 2005-06-25 | IT_PROG    |  4800.00 |                |        103 |            60
         106 | Valli      | Pataballa | VPATABAL | 590.423.4560 | 2006-02-05 | IT_PROG    |  4800.00 |                |        103 |            60
         107 | Diana      | Lorentz   | DLORENTZ | 590.423.5567 | 2007-02-07 | IT_PROG    |  4200.00 |                |        103 |            60
         108 | Nancy      | Greenberg | NGREENBE | 515.124.4569 | 2002-08-17 | FI_MGR     | 12008.00 |                |        101 |           100
         109 | Daniel     | Faviet    | DFAVIET  | 515.124.4169 | 2002-08-16 | FI_ACCOUNT |  9000.00 |                |        108 |           100
(10 rows)

[postgres@localhost ~]$

--查询结果输出到文件
[postgres@localhost ~]$ psql -c 'select * from emp' -o a.log
[postgres@localhost ~]$ cat a.log
 employee_id | first_name | last_name |  email   | phone_number | hire_date  |   job_id   |  salary  | commission_pct | manager_id | department_id
-------------+------------+-----------+----------+--------------+------------+------------+----------+----------------+------------+---------------
         100 | Steven     | King      | SKING    | 515.123.4567 | 2003-06-17 | AD_PRES    | 24000.00 |                |            |            90
         101 | Neena      | Kochhar   | NKOCHHAR | 515.123.4568 | 2005-09-21 | AD_VP      | 17000.00 |                |        100 |            90
         102 | Lex        | De Haan   | LDEHAAN  | 515.123.4569 | 2001-01-13 | AD_VP      | 17000.00 |                |        100 |            90
         103 | Alexander  | Hunold    | AHUNOLD  | 590.423.4567 | 2006-01-03 | IT_PROG    |  9000.00 |                |        102 |            60
         104 | Bruce      | Ernst     | BERNST   | 590.423.4568 | 2007-05-21 | IT_PROG    |  6000.00 |                |        103 |            60
         105 | David      | Austin    | DAUSTIN  | 590.423.4569 | 2005-06-25 | IT_PROG    |  4800.00 |                |        103 |            60
         106 | Valli      | Pataballa | VPATABAL | 590.423.4560 | 2006-02-05 | IT_PROG    |  4800.00 |                |        103 |            60
         107 | Diana      | Lorentz   | DLORENTZ | 590.423.5567 | 2007-02-07 | IT_PROG    |  4200.00 |                |        103 |            60
         108 | Nancy      | Greenberg | NGREENBE | 515.124.4569 | 2002-08-17 | FI_MGR     | 12008.00 |                |        101 |           100
         109 | Daniel     | Faviet    | DFAVIET  | 515.124.4169 | 2002-08-16 | FI_ACCOUNT |  9000.00 |                |        108 |           100
(10 rows)

[postgres@localhost ~]$

--查询结果输出并记录到文件
[postgres@localhost ~]$ psql -c 'select * from emp' -L b.log
 employee_id | first_name | last_name |  email   | phone_number | hire_date  |   job_id   |  salary  | commission_pct | manager_id | department_id
-------------+------------+-----------+----------+--------------+------------+------------+----------+----------------+------------+---------------
         100 | Steven     | King      | SKING    | 515.123.4567 | 2003-06-17 | AD_PRES    | 24000.00 |                |            |            90
         101 | Neena      | Kochhar   | NKOCHHAR | 515.123.4568 | 2005-09-21 | AD_VP      | 17000.00 |                |        100 |            90
         102 | Lex        | De Haan   | LDEHAAN  | 515.123.4569 | 2001-01-13 | AD_VP      | 17000.00 |                |        100 |            90
         103 | Alexander  | Hunold    | AHUNOLD  | 590.423.4567 | 2006-01-03 | IT_PROG    |  9000.00 |                |        102 |            60
         104 | Bruce      | Ernst     | BERNST   | 590.423.4568 | 2007-05-21 | IT_PROG    |  6000.00 |                |        103 |            60
         105 | David      | Austin    | DAUSTIN  | 590.423.4569 | 2005-06-25 | IT_PROG    |  4800.00 |                |        103 |            60
         106 | Valli      | Pataballa | VPATABAL | 590.423.4560 | 2006-02-05 | IT_PROG    |  4800.00 |                |        103 |            60
         107 | Diana      | Lorentz   | DLORENTZ | 590.423.5567 | 2007-02-07 | IT_PROG    |  4200.00 |                |        103 |            60
         108 | Nancy      | Greenberg | NGREENBE | 515.124.4569 | 2002-08-17 | FI_MGR     | 12008.00 |                |        101 |           100
         109 | Daniel     | Faviet    | DFAVIET  | 515.124.4169 | 2002-08-16 | FI_ACCOUNT |  9000.00 |                |        108 |           100
(10 rows)

[postgres@localhost ~]$ cat b.log
********* QUERY **********
select * from emp
**************************

 employee_id | first_name | last_name |  email   | phone_number | hire_date  |   job_id   |  salary  | commission_pct | manager_id | department_id
-------------+------------+-----------+----------+--------------+------------+------------+----------+----------------+------------+---------------
         100 | Steven     | King      | SKING    | 515.123.4567 | 2003-06-17 | AD_PRES    | 24000.00 |                |            |            90
         101 | Neena      | Kochhar   | NKOCHHAR | 515.123.4568 | 2005-09-21 | AD_VP      | 17000.00 |                |        100 |            90
         102 | Lex        | De Haan   | LDEHAAN  | 515.123.4569 | 2001-01-13 | AD_VP      | 17000.00 |                |        100 |            90
         103 | Alexander  | Hunold    | AHUNOLD  | 590.423.4567 | 2006-01-03 | IT_PROG    |  9000.00 |                |        102 |            60
         104 | Bruce      | Ernst     | BERNST   | 590.423.4568 | 2007-05-21 | IT_PROG    |  6000.00 |                |        103 |            60
         105 | David      | Austin    | DAUSTIN  | 590.423.4569 | 2005-06-25 | IT_PROG    |  4800.00 |                |        103 |            60
         106 | Valli      | Pataballa | VPATABAL | 590.423.4560 | 2006-02-05 | IT_PROG    |  4800.00 |                |        103 |            60
         107 | Diana      | Lorentz   | DLORENTZ | 590.423.5567 | 2007-02-07 | IT_PROG    |  4200.00 |                |        103 |            60
         108 | Nancy      | Greenberg | NGREENBE | 515.124.4569 | 2002-08-17 | FI_MGR     | 12008.00 |                |        101 |           100
         109 | Daniel     | Faviet    | DFAVIET  | 515.124.4169 | 2002-08-16 | FI_ACCOUNT |  9000.00 |                |        108 |           100
(10 rows)

[postgres@localhost ~]$


--显示元命令对应 sql
[postgres@localhost ~]$ psql -E
psql (13.6)
Type "help" for help.

postgres=# \l
********* QUERY **********
SELECT d.datname as "Name",
       pg_catalog.pg_get_userbyid(d.datdba) as "Owner",
       pg_catalog.pg_encoding_to_char(d.encoding) as "Encoding",
       d.datcollate as "Collate",
       d.datctype as "Ctype",
       pg_catalog.array_to_string(d.datacl, E'\n') AS "Access privileges"
FROM pg_catalog.pg_database d
ORDER BY 1;
**************************

                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 db1       | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 test      | postgres | UTF8     | C           | C           |
 tpcc      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
(6 rows)

三、交互界面执行 sql 命令

连入交互界面后就可进行正常 sql 语句的执行，示例如下（注意 psql 交互界面执行 sql 结尾必须带分号）：

[postgres@localhost ~]$ psql
psql (13.6)
Type "help" for help.
--建表
postgres=# create table test1(id int,name varchar);
CREATE TABLE
--插入数据
postgres=# insert into test1 values(1,'zhao'),(2,'qian'),(3,'sun');
INSERT 0 3
--查询
postgres=# select * from test1;
 id | name
----+------
  1 | zhao
  2 | qian
  3 | sun
(3 rows)

上述示例中，进入交互界面的提示符 postgres=# 说明：

postgres：当前连接的数据库。
=：交互界面就绪状态，此状态可正常执行命令，异常状态为 -，命令执行异常后为此状态，Ctrl+C 退出异常进入就绪态后，才可正常执行命令。
#：当前连接用户为超级权限用户，普通用户提示符为 >。

--异常操作示例
postgres=# select * from test1
postgres-#
postgres-#
postgres-# ^C
postgres=# select * from test1;
 id | name
----+------
  1 | zhao
  2 | qian
  3 | sun
(3 rows)

--用普通用户切换至其他数据库后的提示符信息
postgres=# \c db1 syd
Password for user syd:
You are now connected to database "db1" as user "syd".
db1=>

四、元命令

  psql 交互界面提供了一系列元命令，方便快捷查询或设置，元命令均以反斜线 \ 开始。大多查询命令后可跟加号 +，更详细地展示查询信息。

4.1 常用查询类

• \c：显示当前连接信息。
• \c dbname：切换连接的数据库。
• \c username：切换连接的用户。
• \c dbname name：切换连接的用户和数据库。
• \l[+]：显示所有数据库信息。
• \du[+]：显示所有用户信息。
• \dn[+]：显示当前数据库下所有模式信息。
• \dx[+]：显示当前数据库下所有扩展信息。
• \dt[+]：显示当前数据库下当前模式下所有表信息。
• \dv[+]：显示当前数据库下当前模式下所有视图信息。
• \di[+]：显示当前数据库下当前模式下所有索引信息。
• \ds[+]：显示当前数据库下当前模式下所有序列信息。
• \df[+]：显示当前数据库下当前模式下所有函数信息。
• \d jobname：显示具体的对象结构，jobname 可为具体的表、视图、索引、序列的名字。
• \h sql：查询 sql 语法。
• 通配符使用：t*，以 t 开头的对象；t??，以 t 开头，长度为三个字符的对象。
• \set：查看当前 psql 环境变量设置。
• \pset：查看当前 psql 输出格式设置。
• \？：显示所有元命令使用介绍。

部分示例：

--显示当前连接信息
postgres=# \c
You are now connected to database "postgres" as user "postgres".
--切换数据库
postgres=# \c db1
You are now connected to database "db1" as user "postgres".
db1=# \c postgres
You are now connected to database "postgres" as user "postgres".
--切换用户
postgres=# \c - syd
Password for user syd:
You are now connected to database "postgres" as user "syd".
postgres=> \c - postgres
You are now connected to database "postgres" as user "postgres".
--切换数据库和用户
postgres=# \c db1 syd
Password for user syd:
You are now connected to database "db1" as user "syd".
db1=> \c postgres postgres
You are now connected to database "postgres" as user "postgres".
--显示所有数据库信息
postgres=# \l
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 db1       | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 test      | postgres | UTF8     | C           | C           |
 tpcc      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
(6 rows)

postgres=# \l+
                                                                    List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   |  Size   | Tablespace |                Description
-----------+----------+----------+-------------+-------------+-----------------------+---------+------------+--------------------------------------------
 db1       | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                       | 7885 kB | pg_default |
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                       | 29 MB   | pg_default | default administrative connection database
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +| 7737 kB | pg_default | unmodifiable empty database
           |          |          |             |             | postgres=CTc/postgres |         |            |
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +| 7737 kB | pg_default | default template for new databases
           |          |          |             |             | postgres=CTc/postgres |         |            |
 test      | postgres | UTF8     | C           | C           |                       | 945 MB  | pg_default |
 tpcc      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                       | 8393 kB | pg_default |
(6 rows)
--显示 emp 表结构
postgres=# \d emp
                           Table "public.emp"
     Column     |         Type          | Collation | Nullable | Default
----------------+-----------------------+-----------+----------+---------
 employee_id    | integer               |           |          |
 first_name     | character varying(20) |           |          |
 last_name      | character varying(25) |           |          |
 email          | character varying(25) |           |          |
 phone_number   | character varying(20) |           |          |
 hire_date      | date                  |           |          |
 job_id         | character varying(10) |           |          |
 salary         | numeric(8,2)          |           |          |
 commission_pct | numeric(2,2)          |           |          |
 manager_id     | integer               |           |          |
 department_id  | integer               |           |          |

postgres=# \d+ emp
                                               Table "public.emp"
     Column     |         Type          | Collation | Nullable | Default | Storage  | Stats target | Description
----------------+-----------------------+-----------+----------+---------+----------+--------------+-------------
 employee_id    | integer               |           |          |         | plain    |              |
 first_name     | character varying(20) |           |          |         | extended |              |
 last_name      | character varying(25) |           |          |         | extended |              |
 email          | character varying(25) |           |          |         | extended |              |
 phone_number   | character varying(20) |           |          |         | extended |              |
 hire_date      | date                  |           |          |         | plain    |              |
 job_id         | character varying(10) |           |          |         | extended |              |
 salary         | numeric(8,2)          |           |          |         | main     |              |
 commission_pct | numeric(2,2)          |           |          |         | main     |              |
 manager_id     | integer               |           |          |         | plain    |              |
 department_id  | integer               |           |          |         | plain    |              |
Access method: heap
--通配符使用
postgres=# \dt t*
          List of relations
 Schema |   Name   | Type  |  Owner
--------+----------+-------+----------
 public | t_gist   | table | postgres
 public | t_spgist | table | postgres
 public | test     | table | postgres
 public | test0509 | table | postgres
 public | test1    | table | postgres
 public | ts       | table | postgres
 public | ttt      | table | postgres
(7 rows)

postgres=# \dt t??
        List of relations
 Schema | Name | Type  |  Owner
--------+------+-------+----------
 public | ttt  | table | postgres
--查询建库语法
postgres=# \h create database
Command:     CREATE DATABASE
Description: create a new database
Syntax:
CREATE DATABASE name
    [ [ WITH ] [ OWNER [=] user_name ]
           [ TEMPLATE [=] template ]
           [ ENCODING [=] encoding ]
           [ LOCALE [=] locale ]
           [ LC_COLLATE [=] lc_collate ]
           [ LC_CTYPE [=] lc_ctype ]
           [ TABLESPACE [=] tablespace_name ]
           [ ALLOW_CONNECTIONS [=] allowconn ]
           [ CONNECTION LIMIT [=] connlimit ]
           [ IS_TEMPLATE [=] istemplate ] ]

URL: https://www.postgresql.org/docs/13/sql-createdatabase.html
--查询插入数据语法
postgres=# \h insert
Command:     INSERT
Description: create new rows in a table
Syntax:
[ WITH [ RECURSIVE ] with_query [, ...] ]
INSERT INTO table_name [ AS alias ] [ ( column_name [, ...] ) ]
    [ OVERRIDING { SYSTEM | USER } VALUE ]
    { DEFAULT VALUES | VALUES ( { expression | DEFAULT } [, ...] ) [, ...] | query }
    [ ON CONFLICT [ conflict_target ] conflict_action ]
    [ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ]

where conflict_target can be one of:

    ( { index_column_name | ( index_expression ) } [ COLLATE collation ] [ opclass ] [, ...] ) [ WHERE index_predicate ]
    ON CONSTRAINT constraint_name

and conflict_action is one of:

    DO NOTHING
    DO UPDATE SET { column_name = { expression | DEFAULT } |
                    ( column_name [, ...] ) = [ ROW ] ( { expression | DEFAULT } [, ...] ) |
                    ( column_name [, ...] ) = ( sub-SELECT )
                  } [, ...]
              [ WHERE condition ]

URL: https://www.postgresql.org/docs/13/sql-insert.html

4.2 常用操作类

• \q：退出交互界面。
• \! command：执行 linux 系统命令。
• \e filename：编辑 linux 上的文件。
• \ev viewname：编辑视图。
• \ef functionname：编辑函数。
• \o：执行结果输出到外部文件，作用同上 psql -o 参数。
• \i：执行存储在操作系统上的外部 sql 文件，作用同上 psql -f 参数。

部分示例：

--退出交互界面
postgres=# \q
[postgres@localhost ~]$

--执行 linux 系统命令
postgres=# \! date
Sun Jun 25 10:11:05 CST 2023

[postgres@localhost ~]$ cat a.log
ssss
[postgres@localhost ~]$ psql
psql (13.6)
Type "help" for help.

postgres=# \e /home/postgres/a.log
ssss
~
~

--编辑视图
postgres=# \d+ emp_v
                                       View "public.emp_v"
     Column     |         Type          | Collation | Nullable | Default | Storage  | Description
----------------+-----------------------+-----------+----------+---------+----------+-------------
 employee_id    | integer               |           |          |         | plain    |
 first_name     | character varying(20) |           |          |         | extended |
 last_name      | character varying(25) |           |          |         | extended |
 email          | character varying(25) |           |          |         | extended |
 phone_number   | character varying(20) |           |          |         | extended |
 hire_date      | date                  |           |          |         | plain    |
 job_id         | character varying(10) |           |          |         | extended |
 salary         | numeric(8,2)          |           |          |         | main     |
 commission_pct | numeric(2,2)          |           |          |         | main     |
 manager_id     | integer               |           |          |         | plain    |
 department_id  | integer               |           |          |         | plain    |
View definition:
 SELECT emp.employee_id,
    emp.first_name,
    emp.last_name,
    emp.email,
    emp.phone_number,
    emp.hire_date,
    emp.job_id,
    emp.salary,
    emp.commission_pct,
    emp.manager_id,
    emp.department_id
   FROM emp;

postgres=# \ev emp_v
CREATE OR REPLACE VIEW public.emp_v AS
 SELECT emp.employee_id,
    emp.first_name,
    emp.last_name,
    emp.email,
    emp.phone_number,
    emp.hire_date,
    emp.job_id,
    emp.salary,
    emp.commission_pct,
    emp.manager_id,
    emp.department_id
   FROM emp
~
~

4.3 常用格式化显示类

• \x：切换查询结果按行展示或列展示模式（默认行展示）。
• \set ECHO_HIDDEN on：显示元命令具体执行的 sql 语句，作用同上 psql -E 参数。

示例：

--切换查询结果行/列展示模式
postgres=# select * from dept;
 department_id | department_name
---------------+-----------------
             1 | Adminstration
             2 | Marketing
            30 | Purchasing
(3 rows)

postgres=# \x
Expanded display is on.
postgres=# select * from dept;
-[ RECORD 1 ]---+--------------
department_id   | 1
department_name | Adminstration
-[ RECORD 2 ]---+--------------
department_id   | 2
department_name | Marketing
-[ RECORD 3 ]---+--------------
department_id   | 30
department_name | Purchasing

postgres=# \x
Expanded display is off.
postgres=# select * from dept;
 department_id | department_name
---------------+-----------------
             1 | Adminstration
             2 | Marketing
            30 | Purchasing
(3 rows)

--显示元命令具体执行 sql
postgres=# \l
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 db1       | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 test      | postgres | UTF8     | C           | C           |
 tpcc      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
(6 rows)

postgres=# \set ECHO_HIDDEN on
postgres=# \l
********* QUERY **********
SELECT d.datname as "Name",
       pg_catalog.pg_get_userbyid(d.datdba) as "Owner",
       pg_catalog.pg_encoding_to_char(d.encoding) as "Encoding",
       d.datcollate as "Collate",
       d.datctype as "Ctype",
       pg_catalog.array_to_string(d.datacl, E'\n') AS "Access privileges"
FROM pg_catalog.pg_database d
ORDER BY 1;
**************************

                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
 db1       | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 test      | postgres | UTF8     | C           | C           |
 tpcc      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
(6 rows)

五、使用技巧

5.1 查询仅显示结果

psql -c -At 返回中仅显示结果，常用于脚本中。

[postgres@localhost ~]$ psql -c  'select * from student;'
 student_no | student_name | age
------------+--------------+-----
          3 | 王二         |  15
          1 | 张三         |  14
(2 rows)

[postgres@localhost ~]$ psql -c  'select * from student;' -At
3|王二|15
1|张三|14

5.2 显示 SQL 执行时间

\timing 元命令用于设置打开或关闭显示 SQL 的执行时间。

postgres=# \timing
Timing is on.
postgres=# select * from student;
 student_no | student_name | age
------------+--------------+-----
          3 | 王二         |  15
          1 | 张三         |  14
(2 rows)

Time: 1.010 ms
postgres=# \timing
Timing is off.
postgres=# select * from student;
 student_no | student_name | age
------------+--------------+-----
          3 | 王二         |  15
          1 | 张三         |  14
(2 rows)

5.3 重复执行当前 sql

\watch [seconds] 元命令会重复当前查询缓冲区的 SQL 命令（即上一条 sql），默认两秒，直至终止或失败。

postgres=# select * from student;
 student_no | student_name | age
------------+--------------+-----
          3 | 王二         |  15
          1 | 张三         |  14
(2 rows)

postgres=# \watch
Tue 11 Jul 2023 05:51:53 PM CST (every 2s)

 student_no | student_name | age
------------+--------------+-----
          3 | 王二         |  15
          1 | 张三         |  14
(2 rows)

Tue 11 Jul 2023 05:51:55 PM CST (every 2s)

 student_no | student_name | age
------------+--------------+-----
          3 | 王二         |  15
          1 | 张三         |  14
(2 rows)

^Cpostgres=# \watch 0.05
Tue 11 Jul 2023 05:52:05 PM CST (every 0.05s)

 student_no | student_name | age
------------+--------------+-----
          3 | 王二         |  15
          1 | 张三         |  14
(2 rows)

Tue 11 Jul 2023 05:52:05 PM CST (every 0.05s)

 student_no | student_name | age
------------+--------------+-----
          3 | 王二         |  15
          1 | 张三         |  14
(2 rows)

5.4 修改 psql 默认规则

~/.psqlrc 文件自定义设置，psql 在连入数据库时，会自动执行该文件中的设置，比如将 psql 默认的自动提交改为手动提交。

--默认自动提交开启
[postgres@localhost ~]$ psql
psql (13.6)
Type "help" for help.

postgres=# \set
AUTOCOMMIT = 'on'
……
……

--配置自动提交关闭
[postgres@localhost ~]$ cat ~/.psqlrc
\set AUTOCOMMIT off
[postgres@localhost ~]$ psql
psql (13.6)
Type "help" for help.

postgres=# \set
AUTOCOMMIT = 'off'
……
……